Flexible dry sprinkler having a differential pressure controller

ABSTRACT

A dry sprinkler includes a flexible tube section that maintains a pressurized fluid, such as a liquid antifreeze solution, between a first end and a second end. A first seal prevents fluid from a supply line from entering the flexible tube section. The first seal is maintained in a sealed position by a pressure of the pressurized fluid. A sprinkler head is coupled to the second end of the flexible tube section, and includes a frame, an output orifice, a deflector, a second seal that seals the output orifice, and a thermally responsive element configured to maintain the second seal in a sealed position when the thermally responsive element is in a non-responsive state. A differential pressure controller maintains a ratio between the pressure of the pressurized fluid in the flexible tube section and a pressure of a supply fluid in the supply line to at least a certain ratio.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/989,316, filed May 25, 2018, which is a continuation of U.S. patentapplication Ser. No. 13/757,448, filed Feb. 1, 2013, which issued asU.S. Pat. No. 9,999,793 on Jun. 19, 2018, and which claims priority toU.S. Provisional Patent Application No. 61/594,972, filed Feb. 3, 2012,both of which are incorporated herein by reference.

FIELD OF THE INVENTION

My invention relates to a dry fire protection sprinkler. In particular,my invention relates to a dry fire protection sprinkler for use in anarea that is exposed to freezing conditions. In addition, my inventionrelates to a dry fire protection sprinkler having a differentialpressure controller.

BACKGROUND OF THE INVENTION

Dry sprinklers are used in areas that are exposed to freezingconditions, such as in freezers or outdoor walkways. In some dry-pipesystems, fluid supply conduits are positioned in a space in which thefluid in the fluid supply conduit is not subject to freezing. A drysprinkler is attached to the fluid supply conduit and extends into aspace in which the fluid would otherwise be subject to freezing.

A typical dry sprinkler comprises a sprinkler head, a tube, a pipeconnector at an inlet end of the tube that connects the inlet end to apipe network of a fire suppression system, a plug seal at the inlet endto prevent water from entering the tube, and an actuating mechanism tomaintain the plug seal at the inlet end. Typically, the sprinkler headis attached to an end of the tube that is opposite to the inlet end ofthe tube. Also, the tube section is conventionally vented to theatmosphere to allow drainage of any condensate that may form in thetube.

Examples of dry sprinklers are generally disclosed in U.S. Pat. No.5,775,431 to Ondracek, and in U.S. Pat. No. 5,967,240 to Ondracek. Asshown generally in these patents, the actuating mechanism of a drysprinkler can be a rod or another similar structure that extends throughthe tube between the sprinkler head and the inlet end to maintain theplug seal at the inlet end. The actuating mechanism includes a thermallyresponsive support element at the sprinkler head that supports the rodand, therefore, the plug seal at the inlet end. In some dry sprinklers,the tube is also sealed at the sprinkler head end of the tube and theactuating mechanism is supported at the sprinkler head end by a seal capthat is supported by the thermally responsive support element. In sucharrangements, the space in the tube between the seal cap and the plugseal can be filled with a pressurized gas, such as dry air or nitrogen,or with a liquid, such as an antifreeze solution. When an elevatedtemperature occurs, the thermally responsive support element fails,releasing the plug seal (and also any lower seal at the sprinkler headend of the tube) to allow water from the fluid supply conduit to flowinto and through the tube to the sprinkler head, whereupon the fluid isdistributed by the sprinkler head.

Conventional dry sprinklers are fabricated using a rigid tube having aseal at the inlet that is separated from the thermally responsivesupport element of the sprinkler, which is intended to be positioned inan area exposed to freezing conditions, such as an area that is notheated. The rigid tube extends into the unheated area from a wet pipesystem (located in a heated area) and must be precisely aligned andinstalled while avoiding various architectural, structural, andmechanical obstructions typically found in commercial or industrialbuildings.

SUMMARY OF THE INVENTION

To remedy the problems and difficulties noted above, in one aspect, theinvention provides a dry sprinkler having a flexible tube section thathas a first end having an inlet opening, and a second end having anoutlet opening. The flexible tube section is configured to contain apressurized fluid between the first end and the second end. Thepressurized fluid includes a liquid anti-freeze solution that is notsusceptible to freezing at the freezing point of water. The drysprinkler includes a supply line connection having a first end connectedto the inlet opening of the first end of the flexible tube section andhaving an opening, and a second end configured to connect to a supplyline to receive a supply fluid from the supply line. A first seal isconfigured to seal the opening at the first end of the supply lineconnection to prevent the supply fluid from the supply line fromentering the flexible tube section. The first seal is maintained in asealed position by a pressure of the pressurized fluid so as to seal theopening at the first end of the supply line connection. A sprinkler headis coupled to the second end of the flexible tube section. The sprinklerhead has a frame connected to the second end of the flexible tubesection, an output orifice centrally located within the frame, adeflector connected to the frame, a second seal configured to seal theoutput orifice of the sprinkler head, and a thermally responsive elementbetween the frame and the second seal. The thermally responsive elementis configured to maintain the second seal in a sealed position when thethermally responsive element is in a non-responsive state. Adifferential pressure controller is connected to the flexible tubesection between the first seal and the second seal, and is connected tothe supply line connection. The differential pressure controller isconfigured to supply the pressurized fluid to the flexible tube sectionin order to maintain a ratio between the pressure of the pressurizedfluid in the flexible tube section and a pressure of the supply fluid inthe supply line to at least a certain ratio. The pressure of thepressurized fluid in the flexible tube section is not equal to thepressure of the supply fluid in the supply line. The thermallyresponsive element is configured to switch from the non-responsive stateto a responsive state to release the second seal in response to anelevated temperature condition, and to permit the release of thepressurized fluid in the flexible tube section. The release of thepressurized fluid in the flexible tube section releases the first sealfrom the seal position.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a flexible dry sprinkler in accordance with an embodimentof the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIG. 1, a flexible dry sprinkler arrangement comprises agenerally flexible tube 1 that is connected at one end to a sprinklerhead 2 and connected at another end to a fitting 3 constructed to becoupled to a wet pipe, a dry pipe, or a preaction fire sprinkler system.The fitting 3 includes an inlet seal assembly having a first seal 4 thatis normally in a closed or sealed position for preventing the flow offluid from the fitting 3 through the flexible tube 1 and the sprinklerhead 2. The flexible tube 1 is also sealed at the sprinkler head 2 by anoutlet seal assembly having a second seal 5 (e.g., a sealing cap) thatis supported by a thermal release element 6 compressed between thesecond seal 5 and a frame 7 of the sprinkler head 2. The first seal 4 isgenerally formed as an annular plug having a grooved outer edge thatsits against an annular spring washer 9 of the inlet seal assembly, suchas a Belleville washer. The annular spring washer 9 is configured toseal with an annular flange 10 extending from an inner wall of thefitting 3. The second seal 5 is formed similarly to the first seal 4,and also is generally formed as an annular disk 11 having an outerannular groove that receives a spring washer 12 of the outlet sealassembly. The spring washer 12 is constructed to seal against a sealingflange 13 formed in an output orifice 14 of the sprinkler head 2.

The flexible tube 1 can be formed from a metallic or a non-metallicmaterial. For example, in one embodiment, the flexible tube 1 is formedfrom a corrugated metal hose, and, in another embodiment, the flexibletube 1 is formed from a corrugated plastic hose. The outer surface ofthe flexible tube 1 can be covered, such as with a braided jacket, toprotect the flexible tube 1. As shown in the preferred embodiment, thesprinkler head 2 has male threads that engage with female threads on theoutput end of the flexible tube 1. The female threaded connection of theflexible tube 1 can have a nominal diameter that is between ½ inch and 1inch. While a specific configuration of the sprinkler head 2 is shown inFIG. 1, the present disclosure is broader than this configuration, andit is contemplated that substantially any present or future approved orlisted fire sprinkler head can be attached to the flexible tube 1 inplace of the sprinkler head 2 shown in FIG. 1.

When the flexible dry sprinkler is in a sealed state, as shown in FIG.1, the flexible dry sprinkler is filled with a fluid that is pressurizedto keep the first seal 4 sealed. The fluid is a freeze resistant gas,such as nitrogen, or a liquid, such as a water/glycol mixture or otherconventional “antifreeze” liquids.

The connection to the fire sprinkler system utilizes a differentialpressure device 16 to ensure the pressure in the flexible tube 1 isgreater than the pressure in the fluid supply so as to prevent theintroduction of water or air from the fire sprinkler system into theflexible tube 1. This differential pressure device 16 is configured tomaintain a ratio of 3 to 1 or greater between the pressure P1 in theflexible tube 1 and the fluid supply pressure P3 in the fluid supply. Itis believed that the ratio of 3 to 1 is sufficient to prevent leakageinto the flexible tube 1 caused by pressure surges in the fluid supplyof the fire sprinkler system. In one embodiment, the differentialpressure device 16 is configured as a differential pressure controllerin communication with a pressure sensor that monitors the fluid supplypressure P3 and in communication with a pressure sensor that monitorsthe pressure P1. The differential pressure controller 16 is incommunication with a control valve 17 positioned between the flexibletube 1 and a source of pressurized fluid 18 that is maintained at apressure P2 that is greater than the fluid supply pressure P3. In theevent that the pressure ratio drops below 3 to 1, a signal is sent fromthe differential pressure controller 16 to the control valve 17 to openthe control valve 17 to introduce the pressurized fluid from the sourceof pressurized fluid 18 into the flexible tube 1 until the 3 to 1 ratiois achieved, at which time the control valve 17 is instructed to close.Thus, the differential pressure controller 16 and the control valve 17operate according to a conventional feedback control arrangement tomaintain the desired pressure ratio, e.g., of 3 to 1. It will beappreciated that the differential pressure controller 16 may include acomputer constructed to execute a computer readable program stored in atangible computer-readable medium or in another type of memory, andincluding instructions for operating the differential pressurecontroller 16 to maintain the pressure ratio between P1 and P3. Whileone embodiment of a control arrangement has been described withreference to the preferred embodiment, other control arrangements can beemployed to maintain the desired pressure ratio, and are within thescope of this disclosure.

Moreover, the various pressure sensors that monitor the pressures P1,P2, and P3 can be constructed to communicate with an alarm system tonotify an operator regarding operation of the fire sprinkler system. Forexample, an alarm may be provided to notify an operator if the pressureP1 decreases to a certain pressure value, which may alert the operatorof the possibility that the sprinkler head 2 may be leaking.Alternatively, notifications can be provided by various methods,including, but not limited to, a telephone message, an e-mail, a visualdisplay, and a facsimile message. Optionally, a visual pressureindicator, such as an analog or digital pressure gauge, locatedproximate to the flexible dry sprinkler, can be installed for indicationthat the pressure P1 of the fluid sealed in the flexible tube 1 has beenmaintained within tolerances permitted by the design of the flexible drysprinkler. Such an indicator may simply be a binary status indicator,such as a color indicator, e.g., an indicator that displays green,indicating acceptable operating status, and that displays red,indicating an unacceptable operating status. Of course, other pressureindicators are within the scope of this disclosure.

An optional flexible linkage 15 is shown in FIG. 1 connecting the firstseal 4 to the second seal 5. The flexible linkage 15 is formed of amaterial that will not corrode in the presence of the fluid contained inthe flexible tube 1. The flexible linkage 15 can be formed as a chain ora cable. In one exemplary embodiment, the flexible linkage 15 isconstructed of stainless steel. By virtue of the flexible linkage 15,when the flexible tube 1 of the flexible dry sprinkler is bent, as shownby the broken lines, the flexible linkage 15 in the flexible tube 1 willconform to the inner wall of the flexible tube 1 and will not limit therange of motion of the flexible tube 1. Also, by physically coupling thefirst seal 4 and the second seal 5 together with the flexible linkage15, the first seal 4 can be pulled out of the flexible tube 1 by virtueof the release and discharge of the second seal 5. It is expected thatthe flexible linkage 15 will positively ensure that the first seal 4 isindeed removed from the path of flow in the flexible tube 1 withoutbeing obstructed by other structures in the flexible tube 1. Also, theflexible linkage 15 allows the first seal 4 to pass out of the flexibletube 1 regardless of any kinks or sharp corners in the inner surface ofthe flexible tube 1 caused by corrugations in the flexible tube 1 orflexing of the flexible tube 1.

The flexibility in the flexible tube 1 of the flexible dry sprinklerfacilitates installation of the sprinkler system because the flexibledry sprinkler can be moved around building obstructions that wouldordinarily require additional plumbing work. Moreover, the flexibilityof the flexible dry sprinkler eliminates the need for installers of thefluid supply to precisely align the sprinkler drops (i.e., theconnections for each flexible dry sprinkler) in the ceiling of astructure because any variance can be adjusted by movement of theflexible tube 1.

While the present invention has been described with respect to what are,at present, considered to be the preferred embodiments, it is to beunderstood that the invention is not limited to the disclosedembodiments. To the contrary, the invention is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

INDUSTRIAL APPLICABILITY

My invention can be used to provide fire protection, particularly inareas subject to freezing conditions. Thus, the invention is applicableto the fire protection industry.

We claim:
 1. A dry fire protection sprinkler comprising: a fitting having (i) an inlet end configured to connect to a fluid supply line that supplies a pressurized fluid, (ii) an inlet orifice, and (iii) an outlet end; an inlet seal assembly having an inlet plug and a spring washer that are configured to seal the inlet orifice of the fitting; a flexible tube having an inlet end connected to the outlet end of the fitting, an outlet end, and a valve opening, and configured to contain a pressurized fluid, wherein the flexible tube has a circular inner cross section and a diameter of the spring washer of the inlet seal assembly is less than an inner diameter of the flexible tube; a sprinkler frame connected to the outlet end of the flexible tube, and having an outlet orifice; an outlet seal assembly having a sealing cap and a spring washer that are configured to seal the outlet orifice of the sprinkler frame, wherein the flexible tube contains the pressurized fluid between the inlet plug of the inlet seal assembly and the sealing cap of the outlet seal assembly; a thermally responsive element provided between the sprinkler frame and the sealing cap of the outlet seal assembly, the thermally responsive element being configured to fail when ambient temperature reaches a predetermined temperature, and to hold the sealing cap of the outlet seal assembly in the outlet orifice until the thermally responsive element fails; a flexible tube pressure sensor configured to measure a pressure P1 of the pressurized fluid in the flexible tube; a control valve connected to the valve opening of the flexible tube, and configured to open and to close; a pressurized fluid source connected to the control valve and configured to supply the pressurized fluid to the flexible tube when the control valve opens, the pressurized fluid in the pressurized fluid source being at a pressure P2; a fluid supply pressure sensor configured to measure a pressure P3 of the pressurized fluid in the fluid supply line, the pressure P2 of the pressurized fluid in the pressurized fluid source being greater than the pressure P3 of the fluid in the supply line; and a differential pressure controller connected to the control valve, to the flexible tube pressure sensor, and to the fluid supply pressure sensor, and, when a ratio of the pressure P1 of the pressurized fluid in the flexible tube to the pressure P3 of the fluid in the fluid supply line is less than a predetermined ratio of at least 3 to 1, the differential pressure controller sends a signal to the control valve to open, in order to allow the pressurized fluid in the pressurized fluid source at the pressure of P2 to enter the flexible tube, and, when the ratio of the pressure P1 of the pressurized fluid in the flexible tube to the pressure P3 of the fluid in the fluid supply line equals the predetermined ratio, the differential pressure controller sends a signal to the control valve to close, wherein the inlet plug of the inlet seal assembly is maintained in the inlet orifice by the pressure of the pressurized fluid, and wherein, when the thermally responsive element fails, the sealing cap of the outlet seal assembly is released, releasing the inlet plug of the inlet seal assembly from the inlet orifice, and permitting the pressurized fluid in the flexible tube to flow through the outlet orifice.
 2. The dry fire protection sprinkler according to claim 1, wherein the sprinkler frame has frame arms that form a hub that is spaced from the outlet orifice.
 3. The dry fire protection sprinkler according to claim 2, further comprising a deflector connected to the hub of the sprinkler frame.
 4. The dry fire protection sprinkler according to claim 1, wherein the outlet end of the flexible tube is threadably connected to the sprinkler frame.
 5. The dry fire protection sprinkler according to claim 1, further comprising a pressure indicator connected to the flexible tube, the pressure indicator being configured to indicate the pressure of the pressurized fluid in the flexible tube.
 6. The dry fire protection sprinkler according to claim 5, wherein the pressure indicator is at least one of an analog pressure monitor and a digital pressure monitor.
 7. The dry sprinkler according to claim 5, wherein the pressure indicator is constructed to communicate with an alarm system.
 8. The dry fire protection sprinkler according to claim 7, wherein the alarm system notifies an operator if the pressure of the pressurized fluid in the flexible tube decreases to a certain pressure value.
 9. The dry fire protection sprinkler according to claim 1, further comprising a flexible connector provided in the flexible tube and connected to the inlet plug of the inlet seal assembly and the sealing cap of the outlet seal assembly.
 10. The dry fire protection sprinkler according to claim 9, wherein the flexible connector is one of a chain and a cable.
 11. The dry fire protection sprinkler according to claim 1, wherein the flexible tube is a corrugated metal hose.
 12. The dry fire protection sprinkler according to claim 1, wherein the flexible tube is a corrugated plastic hose.
 13. The dry fire protection sprinkler according to claim 1, wherein the spring washer of the outlet seal assembly is provided in the outlet orifice of the sprinkler frame, and the sealing cap of the outlet seal assembly is an annular disk that sits in the spring washer of the outlet seal assembly.
 14. The dry fire protection sprinkler according to claim 13, wherein the annular disk of the outlet seal assembly has an annular groove, and the spring washer of the outlet seal assembly is positioned in the annular groove.
 15. A dry fire protection sprinkler comprising: a fitting having (i) an inlet end configured to connect to a fluid supply line that supplies a pressurized fluid, (ii) an inlet orifice, and (iii) an outlet end, wherein the fitting has an inner wall with an annular flange; an inlet seal assembly having an inlet plug and a spring washer that are configured to seal the inlet orifice of the fitting, wherein the spring washer is provided in the inlet orifice, the inlet plug is an annular plug that sits in the spring washer, the annular plug has an annular groove, the spring washer is positioned in the annular groove, and the annular plug extends into both the spring washer of the inlet seal assembly and the annular flange; a flexible tube having an inlet end connected to the outlet end of the fitting, an outlet end, and a valve opening, and configured to contain a pressurized fluid, wherein the flexible tube has a circular inner cross section and a diameter of the spring washer of the inlet seal assembly is less than an inner diameter of the flexible tube; a sprinkler frame connected to the outlet end of the flexible tube, and having an outlet orifice; an outlet seal assembly having a sealing cap and a spring washer that are configured to seal the outlet orifice of the sprinkler frame, wherein the flexible tube contains the pressurized fluid between the inlet plug of the inlet seal assembly and the sealing cap of the outlet seal assembly; a thermally responsive element provided between the sprinkler frame and the sealing cap of the outlet seal assembly, the thermally responsive element being configured to fail when ambient temperature reaches a predetermined temperature, and to hold the sealing cap of the outlet seal assembly in the outlet orifice until the thermally responsive element fails; a flexible tube pressure sensor configured to measure a pressure P1 of the pressurized fluid in the flexible tube; a control valve connected to the valve opening of the flexible tube, and configured to open and to close; a pressurized fluid source connected to the control valve and configured to supply the pressurized fluid to the flexible tube when the control valve opens, the pressurized fluid in the pressurized fluid source being at a pressure P2; a fluid supply pressure sensor configured to measure a pressure P3 of the pressurized fluid in the fluid supply line, the pressure P2 of the pressurized fluid in the pressurized fluid source being greater than the pressure P3 of the fluid in the supply line; and a differential pressure controller connected to the control valve, to the flexible tube pressure sensor, and to the fluid supply pressure sensor, and, when a ratio of the pressure P1 of the pressurized fluid in the flexible tube to the pressure P3 of the fluid in the fluid supply line is less than a predetermined ratio of at least 3 to 1, the differential pressure controller sends a signal to the control valve to open, in order to allow the pressurized fluid in the pressurized fluid source at the pressure of P2 to enter the flexible tube, and, when the ratio of the pressure P1 of the pressurized fluid in the flexible tube to the pressure P3 of the fluid in the fluid supply line equals the predetermined ratio, the differential pressure controller sends a signal to the control valve to close, wherein the inlet plug of the inlet seal assembly is maintained in the inlet orifice by the pressure of the pressurized fluid, and wherein, when the thermally responsive element fails, the sealing cap of the outlet seal assembly is released, releasing the inlet plug of the inlet seal assembly from the inlet orifice, and permitting the pressurized fluid in the flexible tube to flow through the outlet orifice.
 16. The dry fire protection sprinkler according to claim 15, wherein the sprinkler frame has frame arms that form a hub that is spaced from the outlet orifice.
 17. The dry fire protection sprinkler according to claim 16, further comprising a deflector connected to the hub of the sprinkler frame.
 18. The dry fire protection sprinkler according to claim 15, wherein the outlet end of the flexible tube is threadably connected to the sprinkler frame.
 19. The dry fire protection sprinkler according to claim 15, further comprising a pressure indicator connected to the flexible tube, the pressure indicator being configured to indicate the pressure of the pressurized fluid in the flexible tube.
 20. The dry fire protection sprinkler according to claim 19, wherein the pressure indicator is at least one of an analog pressure monitor and a digital pressure monitor.
 21. The dry sprinkler according to claim 19, wherein the pressure indicator is constructed to communicate with an alarm system.
 22. The dry fire protection sprinkler according to claim 21, wherein the alarm system notifies an operator if the pressure of the pressurized fluid in the flexible tube decreases to a certain pressure value.
 23. The dry fire protection sprinkler according to claim 15, further comprising a flexible connector provided in the flexible tube and connected to the inlet plug of the inlet seal assembly and the sealing cap of the outlet seal assembly.
 24. The dry fire protection sprinkler according to claim 23, wherein the flexible connector is one of a chain and a cable.
 25. The dry fire protection sprinkler according to claim 15, wherein the flexible tube is a corrugated metal hose.
 26. The dry fire protection sprinkler according to claim 15, wherein the flexible tube is a corrugated plastic hose.
 27. The dry fire protection sprinkler according to claim 15, wherein the spring washer of the outlet seal assembly is provided in the outlet orifice of the sprinkler frame, and the sealing cap of the outlet seal assembly is an annular disk that sits in the spring washer of the outlet seal assembly.
 28. The dry fire protection sprinkler according to claim 27, wherein the annular disk of the outlet seal assembly has an annular groove, and the spring washer of the outlet seal assembly is positioned in the annular groove.
 29. A dry fire protection sprinkler for use in an area that is exposed to freezing conditions, the dry fire protection sprinkler comprising: a fitting having (i) an inlet end configured to connect to a fluid supply line that supplies a pressurized fluid, (ii) an inlet orifice, and (iii) an outlet end; an inlet seal assembly having an inlet plug and a spring washer that are configured to seal the inlet orifice of the fitting; a flexible tube having an inlet end connected to the outlet end of the fitting, an outlet end, and a valve opening, and configured to contain a pressurized fluid, the pressurized fluid being a liquid anti-freeze solution that is not susceptible to freezing at the freezing point of water, wherein the flexible tube has a circular inner cross section and a diameter of the spring washer of the inlet seal assembly is less than an inner diameter of the flexible tube; a sprinkler frame connected to the outlet end of the flexible tube, and having an outlet orifice; an outlet seal assembly having a sealing cap and a spring washer that are configured to seal the outlet orifice of the sprinkler frame, wherein the flexible tube contains the pressurized fluid between the inlet plug of the inlet seal assembly and the sealing cap of the outlet seal assembly; a thermally responsive element provided between the sprinkler frame and the sealing cap of the outlet seal assembly, the thermally responsive element being configured to fail when ambient temperature reaches a predetermined temperature, and to hold the sealing cap of the outlet seal assembly in the outlet orifice until the thermally responsive element fails; a flexible tube pressure sensor configured to measure a pressure P1 of the pressurized fluid in the flexible tube; a control valve connected to the valve opening of the flexible tube, and configured to open and to close; a pressurized fluid source connected to the control valve and configured to supply the pressurized fluid to the flexible tube when the control valve opens, the pressurized fluid in the pressurized fluid source being at a pressure P2; a fluid supply pressure sensor configured to measure a pressure P3 of the pressurized fluid in the fluid supply line, the pressure P2 of the pressurized fluid in the pressurized fluid source being greater than the pressure P3 of the fluid in the supply line; and a differential pressure controller connected to the control valve, to the flexible tube pressure sensor, and to the fluid supply pressure sensor, and, when a ratio of the pressure P1 of the pressurized fluid in the flexible tube to the pressure P3 of the fluid in the fluid supply line is less than a predetermined ratio of at least 3 to 1, the differential pressure controller sends a signal to the control valve to open, in order to allow the pressurized fluid in the pressurized fluid source at the pressure of P2 to enter the flexible tube, and, when the ratio of the pressure P1 of the pressurized fluid in the flexible tube to the pressure P3 of the fluid in the fluid supply line equals the predetermined ratio, the differential pressure controller sends a signal to the control valve to close, wherein the inlet plug of the inlet seal assembly is maintained in the inlet orifice by the pressure of the pressurized fluid, and wherein, when the thermally responsive element fails, the sealing cap of the outlet seal assembly is released, releasing the inlet plug of the inlet seal assembly from the inlet orifice, and permitting the pressurized fluid in the flexible tube to flow through the outlet orifice.
 30. The dry fire protection sprinkler according to claim 29, wherein the sprinkler frame has frame arms that form a hub that is spaced from the outlet orifice.
 31. The dry fire protection sprinkler according to claim 30, further comprising a deflector connected to the hub of the sprinkler frame.
 32. The dry fire protection sprinkler according to claim 29, wherein the outlet end of the flexible tube is threadably connected to the sprinkler frame.
 33. The dry fire protection sprinkler according to claim 29, further comprising a pressure indicator connected to the flexible tube, the pressure indicator being configured to indicate the pressure of the pressurized fluid in the flexible tube.
 34. The dry fire protection sprinkler according to claim 33, wherein the pressure indicator is at least one of an analog pressure monitor and a digital pressure monitor.
 35. The dry sprinkler according to claim 33, wherein the pressure indicator is constructed to communicate with an alarm system.
 36. The dry fire protection sprinkler according to claim 35, wherein the alarm system notifies an operator if the pressure of the pressurized fluid in the flexible tube decreases to a certain pressure value.
 37. The dry fire protection sprinkler according to claim 29, further comprising a flexible connector provided in the flexible tube and connected to the inlet plug of the inlet seal assembly and the sealing cap of the outlet seal assembly.
 38. The dry fire protection sprinkler according to claim 37, wherein the flexible connector is one of a chain and a cable.
 39. The dry fire protection sprinkler according to claim 29, wherein the flexible tube is a corrugated metal hose.
 40. The dry fire protection sprinkler according to claim 29, wherein the flexible tube is a corrugated plastic hose.
 41. The dry fire protection sprinkler according to claim 29, wherein the spring washer of the outlet seal assembly is provided in the outlet orifice of the sprinkler frame, and the sealing cap of the outlet seal assembly is an annular disk that sits in the spring washer of the outlet seal assembly.
 42. The dry fire protection sprinkler according to claim 41, wherein the annular disk of the outlet seal assembly has an annular groove, and the spring washer of the outlet seal assembly is positioned in the annular groove. 